When:11:55 AM 14/May/2022
Who: N. Kimura (ICRR) and T. Tomaru (NAOJ)
Task:
Due to rudimentary mistakes about cryocooler positions of the cryostat,
we turned "OFF" two cryocoolers for EXC at 11:55AM.
The two cryocoolers that were operated were for payload cooling.

The reason for the error was a misreading of the assembly drawings
and the fact that the ports for connecting the cryocoolers were managed by flange numbers of the ports to which they were connected.

This wrong operation caused the mirror of the payload to be cooled by about 7 K.
In order to prevent such mistakes, four cryocooler units which connected yo the cryostat will be changed to be managed by function instead of flange number.

Cooling of the radiation shield will be resumed after confirming the integrity of the payload.